The present invention relates to hinge mechanisms for vehicle seats and to seats fitted with such mechanisms.
More particularly, the invention relates to a vehicle seat hinge mechanism comprising:
first and second rigid structures mounted to pivot relative to each other about a pivot axis;
a set of teeth secured to the first structure and forming at least a circular arc centered on the pivot axis;
at least one toothed locking member mounted on the second structure with substantially no play in a circumferential direction so long as the hinge mechanism is not subjected to a torque in excess of a certain normal value, the locking member being movable in a substantially radial direction between firstly an active position in which said locking member engages the teeth of the first structure to prevent the first and second structures moving relative to each other, and secondly a retracted position in which said locking member does not interfere with the teeth of the first structure (for example, the locking member can slide in the radial direction, or where appropriate it can pivot about an axis situated at the end of a lever arm, in which case the toothed portion of the locking member can follow a curved trajectory tangential to the radial direction); and
a control device suitable for selectively placing the locking member either in its active position or else in its retracted position.
Document EP-A-0 720 930 describes an example of such a hinge mechanism, which gives entire satisfaction. Nevertheless, given progress in safety standards which are becoming ever more severe, it can be useful in some cases to further increase the strength of hinge mechanisms of the above-mentioned type in order to avoid, as much as possible, any breakage of such mechanisms in the event of an accident, with said hinge mechanisms then being subjected to rotary torques that are particularly high.
For this purpose, according to the invention:
the mechanism further comprises at least one blocking member having teeth adapted to engage with the teeth of the first structure, said blocking member being mounted on the second structure in such a manner that its teeth leave a certain amount of clearance in the circumferential direction, the blocking member being movable between firstly an active position in which said blocking member engages the teeth of the first structure, and secondly a retracted position in which said blocking member does not interfere with the teeth of the first structure;
the control device is adapted simultaneously to place the blocking member and the locking member either in the active position or else in the retracted position; and
the second structure has a least one guide which is normally separated from the blocking member by said circumferential clearance, the guide being adapted to co-operate with a projecting side bearing edge belonging to the blocking member to press said blocking member by the wedge effect against the teeth of the first structure when the hinge mechanism is subjected to a torque which greater than said normal value and which absorbs said circumferential clearance of the blocking member by moving the blocking member towards its guide.
By means of these dispositions, locking of the hinge mechanism is reinforced by the blocking member in the event of said mechanism being subjected to a high rotary torque. In addition, the circumferential clearance of the blocking member relative to the second structure makes it possible not only to move the blocking member towards its retracted position under normal circumstances in spite of the projecting bearing edge of the blocking member, but also to guarantee that the blocking member is properly engaged with the teeth of the first structure so long as said blocking member is not in its retracted position.
In preferred embodiments of the invention, use may optionally be made of one or more of the following dispositions:
the second structure has two guides on either side of the blocking member and normally separated from the blocking member by said circumferential clearance, said guides being adapted to co-operate respectively with the two bearing edges belonging to the blocking member by pressing the blocking member by the wedge effect against the teeth of the first structure when the hinge mechanism is subjected to a torque that is greater than said normal value and that absorbs said circumferential clearance of the blocking member;
the blocking member is mounted to slide in a substantially radial direction between its two guides, the guides having respective bearing zones substantially in point contact with the locking member, leaving said locking member with a certain amount of angular clearance, which angular clearance corresponds to said circumferential clearance of the teeth of the blocking member;
the bearing edge of the blocking member co-operates with the teeth of said blocking member to form a wedge that projects sideways relative to said blocking member;
the guide of the blocking member co-operates with the teeth of the first structure to define a wedge-shaped space which opens towards the corresponding bearing edge of the blocking member;
the control device comprises:
a rotary cam which is urged resiliently towards a rest position in which said cam places the locking member in its active position; and
at least one control plate which is secured to the cam and which overlies the locking member and the blocking member at least in part, said control plate having cutouts adapted to co-operate with projecting pegs formed on the locking member and on the blocking member so as to displace said locking member and said blocking member simultaneously towards their retracted positions when the cam is moved into an actuation position;
the blocking member is urged towards its active position by a spring connecting said blocking member to the second structure;
the cutout of the control plate has a ramp-shaped camming edge which is adapted to hold the blocking member in its active position when the cam is in its actuation position;
the control device comprises:
a rotary cam which is urged resiliently towards a rest position in which said cam places the locking member in its active position; and
at least one control plate which is secured to the cam and which overlies the locking member and the blocking member at least in part, said control plate having a cutout adapted to co-operate with a projecting peg provided on the locking member so as to move said locking member towards its retracted position when the cam is moved into an actuation position, said control plate also having a camming edge adapted to co-operate with a projecting peg provided on the blocking member so as to move said blocking member into its active position when the cam is moved into its actuation position, the blocking member being urged resiliently towards its retracted position;
the blocking member is urged resiliently towards its retraced position by a resilient member which bears against the teeth of the first structure;
the resilient member comprises a bearing plate in the form of a circular sector which bears against the teeth of the first structure, and at least one resilient tab secured to the bearing plate and engaged in a hole formed in the blocking member;
the resilient member is a spring wire having at least one circularly-arcuate outer segment bearing against the teeth of the first structure, said circularly-arcuate segment being extended by at least one branch folded as a hairpin and terminated by an end which is engaged in a recess in the blocking member;
the resilient member has two circularly-arcuate segments interconnected by a V-shaped reentrant portion, each of the circularly-arcuate segments being extended by a respective branch folded as a hairpin and terminated by turns wound about an axis parallel to the pivot axis and engaged in a recess formed in the blocking member, at least one of the windings being engaged with clearance in the corresponding recess;
the hinge mechanism comprises:
two diametrically-opposite locking members; and
two blocking members that are likewise diametrically-opposite and that are disposed substantially at right angles relative to the two locking members;
a blocking member and two locking members disposed symmetrically relative to the blocking member, the blocking member forming an angle relative to each locking member where said angle lies in the range 100xc2x0 to 170xc2x0 about the pivot axis;
the control device comprises a rotary cam which is resiliently urged towards a rest position in which said cam holds the locking members in the active position, the cam having first, second, and third bearing edges projecting radially outwards and distributed around he pivot axis, the first and second bearing edges of the cam being adapted to bear against the locking members when the cam is in the rest position, and the third bearing edge of the cam being disposed symmetrically relative to the first and second bearing edges and being adapted to bear radially against an abutment secured to the second structure when the cam is in the rest position, said abutment limiting the movement of the blocking member.
The invention also provides a vehicle seat having a seat proper and a seat-back that are interconnected by at least hinge mechanism as defined above.